Comparing a Group-based Guided Self-help Approach to Pure Self-help for the Treatment of BED

This will be measured using the global score generated from the Binge Eating Scale (BES). The BES is a 16-item measure, each item has 3-4 coded responses. The total score ranges from 0-46, where a higher score indicates greater binge eating severity.

Self reported changes in Binge Eating Frequency over past 28 days will be measured using Item 15 from the Eating Disorder Examination Questionnaire 6.0 (EDE-Q; Fairburn \& Beglin, 1994) which inquires about the number of days with objective binge episodes over the past 28 days.

Self reported changes in Eating Disorder Symptomology will be measured using the global score generated from the EDE-Q (Fairburn \& Beglin, 1994). The EDE-Q is a 28-item measure that assesses four areas of eating disorder psychopathology (eating concern, shape concern, weight concern, dietary restraint). Each item uses a Likert scale ranging from 0 (lowest frequency/severity) to 6 (highest frequency/severity). The global score ranges from 0-6 where higher scores indicate greater impairment. The global score is obtained using the mean of the four subscales.

Self reported changes in clinical impairment will be measured using the Clinical Impairment Assessment Questionnaire (CIA; Bohn \& Fairburn, 2008). This is a 16-item self-report measure of the severity of psychosocial impairment due to eating disorder features over the past 28 days. Each item is ranked on a 0-3 scale (0 being "not at all" and 3 being "a lot"). Total scores range from 0-48, with higher scores indicating greater clinical impairment.

Confidence to Change Binge Eating will be measured using the question, "On a scale from 1 to 10, how confident are you that you can change your binge eating if you wanted to?", with higher scores indicating greater confidence. This question assesses perceived confidence in ability to change binge eating.

Abstinence is defined as a 100% reduction in binge episodes in the 28 days prior to collecting outcome measures.

Remission is defined as meeting criteria for abstinence (100% reduction in binge episodes in the 28 days prior to collecting outcome measures) in addition to having EDEQ global score less than or equal to 2.77 (Fairburn \& Beglin, 1994).

Intervention adherence for participants in the BFT group will be based on session attendance. Completers will be defined as anyone who completes Session 1 and at least one other session. Adherence questionnaires at Week 6 and Week 10 time points inquire about which aspects of the intervention outside of the sessions have been used.

Intervention adherence for participants in the CBT USH group will be calculated using questionnaires provided at both the Week 6 and Week 10 time points that inquire about which chapters have been read and which "CBT Steps" have been completed thus far. Completers will be defined as anyone who indicates that they have read Chapters 1, 4, 5, and 'Getting Ready', and completed Step 1 through Step 3.

This will be measured using the Credibility and Expectancy Questionnaire (CEQ; Devilly \& Borkovec, 2000). The CEQ is a six item self-report measure that measures treatment expectancy and rationale credibility of therapeutic interventions. Each item is scored on a 1-9 Likert-type scale or as a percentage rating from 0% to 100% in increments of 10%. Higher scores indicate greater credibility/expectancy of the intervention.

Participants in both groups will respond to developed Likert-style and open-ended questions asking about their perceptions of their assigned program. Each Likert item is ranked on a scale from 1-9. Higher total scores indicate greater satisfaction with the intervention.